1. Field
Example embodiments of the present invention relate to a touch sensing substrate and a method of manufacturing the touch sensing substrate. More particularly, example embodiments of the present invention relate to a touch sensing substrate capable of improving process reliability and a method of manufacturing the touch sensing substrate.
2. discussion of the Background
In the field of liquid crystal display (LCD) panels, a touch display panel having an input function in addition to displaying an image has been developed with the touch display panel including a sensing element to sense a touch position. Specifically, the touch display panel may include a first substrate on which pixel electrode(s) display the image and a switching element connected to the pixel electrode are formed, a second substrate on which a sensing element detecting light and a driving element controlling the sensing element are formed, and a liquid crystal layer disposed between the display substrate and the touch sensing substrate.
If an external touch is applied on the touch display panel, a light becomes incident to the sensing element and a photo current is generated in the sensing element by the incident light. A detecting circuit electrically connected to the touch display panel detects a touch position using a difference between the photo current and a dark current of the sensing element, the dark current being determined before the incident light is absorbed.
The touch sensing substrate may include a first light sensing element to sense a first light and a second light element to sense a second light. Since the first and second light sensing elements sense lights different from each other, the first and second light sensing elements have active patterns including semiconductor materials different from each other so as to decrease a sensing noise. Thus, the first light sensing element is formed, and then the second light sensing element is formed on the touch sensing substrate on which the first light sensing element is formed.
In a method of manufacturing the light sensing element, the semiconductor material is patterned using a first photolithography process to form an active pattern on a base substrate. A source electrode and a drain electrode are formed on the base substrate on which the active pattern formed, using a second photolithography process. The active pattern has a non-uniform side profile due to the first photolithography process, which may cause defects. For example, defects of the non-uniform side profile may include a tip which remains from the un-etched insulating layer covering the active pattern, a stringer due to an un-covered active pattern by an etch stopping layer, etc. Another defect may be that because the source and drain electrodes are formed after forming the active pattern, the source and drain electrodes may be a short circuit due to the non-uniform side profile of the active pattern.